Use heredoc for outputting help text in automated commit scripts

Summary:
This improves readability and makes reviews easier, as multiline
changes will not add or remove a bunch of kruft in addition to the help contents.

Test Plan:

./autopatch.sh -h
./automated-commits.sh -h

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D7482